refactor field parsing

- make the parsing more straight forward
- be less destructive (keep trailing whitespace)
- empty values will now yield '' and not nil

lib/pdf_forms/field.rb

@@ -9,33 +9,35 @@ class Field
     # FieldStateOption: Ja
     # FieldStateOption: Off
     #
-    # Represenation of a PDF Form Field
+    # Representation of a PDF Form Field
     def initialize(field_description)
       last_value = nil
       field_description.each_line do |line|
-        case line
-        when /FieldStateOption:\s*(.*?)\s*$/
-          (@options ||= []) << $1
-        else
-          line.strip!
-          key, value = line.split(": ", 2)
-          if key and key.gsub!(/Field/, "")
-            key = key.split(/(?=[A-Z])/).map(&:downcase).join('_').split(":")[0]
+        line.chomp!
+
+        if line =~ /^Field([A-Za-z]+):\s+(.*)/
+          _, key, value = *$~
+
+          if key == 'StateOption'
+            (@options ||= []) << value
 
+          else
+            value.chomp!
+            last_value = value
+            key = key.split(/(?=[A-Z])/).map(&:downcase).join('_')
             instance_variable_set("@#{key}", value)
 
             # dynamically add in fields that we didn't anticipate in ATTRS
             unless self.respond_to?(key.to_sym)
               proc = Proc.new { instance_variable_get("@#{key}".to_sym) }
               self.class.send(:define_method, key.to_sym, proc)
             end
-            last_value = value
-          else
-
-            # pdftk returns a line that doesn't start with "Field"
-            # It happens when a text field has multiple lines
-            last_value << "\n" << line
           end
+
+        else
+          # pdftk returns a line that doesn't start with "Field"
+          # It happens when a text field has multiple lines
+          last_value << "\n" << line
         end
       end
     end

test/field_test.rb

@@ -25,8 +25,8 @@ def test_init_with_choice
     assert_equal 'SomeChoiceField', f.name
     assert_equal ['', '010 Foo Bar', 'Another option (xyz)'], f.options
 
-    assert_equal "http://github.com foo", f.value
-    assert_equal nil, f.value_default
+    assert_equal "http://github.com foo ", f.value
+    assert_equal '', f.value_default
     assert_equal "Left", f.justification
     assert_equal "71696384", f.flags
   end